1. Field of the Invention
The present invention relates to a controller of a label printer using an electronic photographic system which makes printing on a continuous printing paper on which a multiplicity of label papers are successively affixed.
2. Description of the Relevant Art
A label printer is known which can print successively on a continuous printing paper on which a multiplicity of label papers are successively affixed.
In this type of label printer, in order to make printing on predetermined positions of the label paper arranged lengthwise of the continuous printing paper at regular intervals, it is very important to exactly control operation timings for various portions, for example, an operation start timing of a printing mechanism for the label paper, a cut timing of a cutter mechanism and the like.
Heretofore, as means for controlling the operation timing, there is known an apparatus disclosed in Japanese Patent Application Laid-Open No. 53-8138 in which feeding holes are formed in both sides of the continuous printing paper lengthwise thereof at regular intervals and pins or teeth of a sprocket are engaged with the feeding holes to move the printing paper so that a rotary angle of the sprocket is controlled to control the position of the continuous printing paper. Alternatively, there is known an apparatus in which the feeding holes of the continuous printing paper are detected by an optical sensor to detect the position thereof.
In the above conventional timing control method, however, it is necessary to use the continuous printing paper in which holes are formed and further there is a limit in the accuracy of the detection of the position.
In the continuous printing paper on which a multiplicity of label papers are successively affixed, an optical sensor can be directly utilized to detect the position of the label paper. More particularly, there is a difference in thickness between an unaffixed paper portion of the printing paper on which the label paper is not affixed and an affixed paper portion of the printing paper on which the label paper is affixed and accordingly a difference in the transmissivity of light can be detected by an optical sensor. However, on the contrary, since the difference of the transmissivity is detected, if there is variation in the thickness of the continuous printing paper and the label paper or the difference in the transmissivity is not so large or further kinds of printing paper and label paper are different, the detection of the difference is impossible or remarkably unstable.